A resin encapsulation type semiconductor device makes use of a lead frame upon its manufacture. The lead frame is fabricated by forming a metal plate as a desired pattern by punching using a precision press or etching. The lead frame has a support portion called a “tub or the like” for fixing a semiconductor chip, and a plurality of leads whose leading ends (internal ends) face the periphery of the support portion. The tub is supported by tub-suspension leads which extend from a frame portion of the lead frame.
When the resin encapsulation type semiconductor device is fabricated through the use of such a lead frame, the semiconductor chip is fixed to the tub of the lead frame, and electrodes of the semiconductor chip and leading ends of the leads are connected to one another by conductive wires. Afterwards, the lead internal-end side including the wires and the semiconductor chip is sealed with an insulating resin to thereby form an encapsulater (package). Further, an unnecessary lead frame portion is removed by cutting, and the leads and tub-suspension leads protruding from the package are cut. Each of the leads is brought to a flat state or processed into a predetermined shape.
As technologies for solving a problem as to a transfer mold for forming a resin encapsulation package, there are known technologies described in Unexamined Patent Publication Nos. Hei 5(1993)-326799, 2000-61989 and Hei 5(1993)-299455, for example.
Although a resin injection hole (gate) is not illustrated in the drawing in the above technologies, the prior art set forth as a premise has described that the resin injection hole is provided in a lower mold. Accordingly, a resin (called “gate cured resin”) cured at a gate portion extends on one surface side of a lead frame so as to have a predetermined height.
Unexamined Patent Publication No. 2000-61989 has disclosed the technology of separating a runner from a molded plastic package with being flush with the package upon a transfer mold process. Namely, a transfer mold die has a movable gate lowered so as to make contact with the plastic package formed at a resin inlet for the cavity on the same plane as the plastic package before the resin is cured after having been injected in the cavity. Accordingly, the runner can be cut on a flush basis with the plastic package.
The same reference has described that when the resin cured within the runner is removed, the resin cured at the runner portion remains at each edge of the plastic package, and a bottleneck is produced in the subsequent lead formation and trimming process due to such a remainder. Problems will be quoted from the same reference and described below.
(1) Damage is put on the trimming of each lead and the formation of a die, and manufacturing yields and a production throughput are reduced. It is necessary to repair or fix up an expensive die.
(2) There is a possibility that upon lead trimming and forming processes, the plastic package will be peeled off from the lead frame, thereby causing a problem about the reliability of a completed product.
(3) The adhesion of the remainder or remaining materials to the plastic package as it is will lead to a serious result. Described typically, a check is made to respective packages and all the remaining materials are manually removed. Therefore, personnel costs increase and a manufacturing throughput is reduced.
According to the present technology, runner's fragments are not left behind with being attached to the plastic package even after the transfer mold. Further, the runner can be detached from the molded lead frame. Thus the work of manually removing the remainder becomes unnecessary. It is also possible to avoid damage to the trimming of each lead and a lead forming instrument due to the remainder as well as to avoid damage to a packaged semiconductor device.
The present technology shows the technical idea that since the remainder of the resin produces a bottleneck in the trimming process such as the bending of each lead, the occurrence of the remainder in the lead frame is avoided even after the removal of the runner. The present technology has no description about the cutting of leads at a gate portion, i.e., a basal portion of the package and makes little mention of such a problem.
Unexamined Patent Publication No. Hei 5(1993)-299455 describes the technology of thinning a gate in stepped form in advance at a base of a resin encapsulated portion so that when a resin portion cured at a gate portion for forming the resin molded portion is separated from a package, a gate residual is not much left on a placed piece or fragment, and causing a gate cured resin to remain on the placed piece thinner or shorter upon removal of the gate cured resin.
The present technology does not show the idea of cutting a placed-fragment portion causing the remainder of the gate.
On the other hand, as one resin encapsulation type semiconductor device fabricated using a lead frame, there is known a non-leaded type semiconductor device such as an SON, a QFN or the like adopted or taken as a semiconductor device structure wherein one surface of the lead frame is single-sided molded to thereby form a package, and leads corresponding to external electrode terminals are exposed to the mounting surface side of the package, thereby avoiding the intentional protrusion of the leads from the peripheral surface of the package.